EP3366713B1 - Method for production of wood composite products - Google Patents

Description

• Bereitstellen eines thermisch härtbaren Harzes, indem man eine polykondensationsfähige phenolische Verbindung und/oder einen Aminoplastbildner mit 5-Hydroxymethylfurfural (HMF) unter zur Bildung von Polykondensationsprodukten führenden Bedingungen umsetzt,
• Inkontaktbringen des Harzes mit lignocellulosehaltigem Material, und
• Aushärten des Harzes unter Bildung des Holzverbundwerkstoffs.

The present invention relates to a method for producing wood composite materials. In particular, the invention relates to a method for producing wood composite materials comprising the steps:

• Providing a thermally curable resin by reacting a polycondensation-capable phenolic compound and / or an aminoplast former with 5-hydroxymethylfurfural (HMF) under conditions leading to the formation of polycondensation products,
• Contacting the resin with lignocellulose-containing material, and
• Hardening the resin to form the wood composite.

Wood composites are typically made from lignocellulosic material such as wood shavings, wood fibers or wood chips and a thermally curable resin. Examples of thermally curable resins are amino resins with the aminoplast formers urea, melamine and dicyandiamide, phenolic resins or amino-phenolic resins. The wood composite materials are usually obtained by contacting the lignocellulose-containing material with the resins and pressing at elevated temperatures, the resins being cured, which is associated with crosslinking.

The US 4,524,164 A. relates to a formaldehyde-free thermosetting adhesive resin and a method of using the adhesive resin for binding lignocellulosic material to form products such as plywood and particle board. First, a liquid meltable resin is prepared by heating an aqueous sugar or starch solution in the presence of a crosslinking agent selected from urea or a phenol or mixtures thereof with an inorganic acid or its ammonium salt and a metal ion catalyst. The meltable resin is then mixed with an organic acid anhydride and applied to the surface of the lignocellulosic material. The mixture is then subjected to heat and pressure to form products such as plywood or chipboard.

The wood composites produced with the resins find their practical application due to their good mechanical properties such as a good internal bond (IB) and insensitivity to moisture, especially to water vapor, especially in furniture construction, where they are used, for example, in the form of plywood, fiber composite, chip - and multilayer boards are used. There they are mainly used indoors. For this reason, it is important that the wood composite materials do not emit harmful compounds. The harmful compounds come mainly from the resins used.

Thermally curable resins are generally obtained by the polycondensation of phenolic compounds and / or aminoplast formers with reactive carbonyl compounds, in particular aldehydes. Due to its high reactivity, the formaldehyde that is classified as hazardous to health is mainly used for the polycondensation. To promote the implementation, an excess of formaldehyde is often used, so that the resins have a high content of free, volatile formaldehyde. The formaldehyde emission of the resins and the wood composite materials produced with them is therefore also high.

Due to the hazard potential, efforts have been made for years to reduce the formaldehyde content. One measure here is to replace formaldehyde with other reactive compounds in the manufacture of the resins. 5-hydroxymethylfurfural (HMF) has already been identified as a promising candidate because it has the ability to form cross-linking bonds, is non-volatile, practically non-toxic and can be obtained from renewable raw materials.

The European Journal of Wood Products describes an HMF-modified urea-formaldehyde resin, in the production of which up to about 30% by weight of the formaldehyde has been replaced by purified, crystalline HMF (N. Esmaeili et al., DOI 10.1007 / s0017- 016-1072-8). Particle boards made with this resin have an internal bond (IB) of ≥ 0.35 N / mm ² , as is currently required to meet the minimum standard for indoor boards in accordance with the European standard NEN EN 319. However, it is disadvantageous that the resin and particle board made from it still contain considerable amounts of toxic formaldehyde.

The object of the present invention is therefore to eliminate the disadvantages mentioned above.

According to a first aspect of the present invention, this is achieved by a method for producing wood composite materials according to the features of claim 1.

• Bereitstellen eines thermisch härtbaren Harzes, indem man eine polykondensationsfähige phenolische Verbindung und/oder einen Aminoplastbildner mit 5-Hydroxymethylfurfural (HMF) unter zur Bildung von Polykondensationsprodukten führenden Bedingungen umsetzt,
• Inkontaktbringen des Harzes mit lignocellulosehaltigem Material, und
• Aushärten des Harzes unter Bildung des Holzverbundwerkstoffs.

The process for producing wood composite materials includes the steps:

• Providing a thermosetting resin by using a polycondensation phenolic compound and / or an aminoplast former with 5-hydroxymethylfurfural (HMF) under conditions leading to the formation of polycondensation products,
• Contacting the resin with lignocellulose-containing material, and
• Hardening the resin to form the wood composite.

The process is characterized in that the 5-hydroxymethylfurfural comprises at least one HMF oligomer.

It has been found that formaldehyde can be dispensed with for the production of wood composite materials, provided that HMF containing HMF oligomers is used for the polycondensation in the preparation step. The HMF oligomers are believed to be more reactive than HMF monomers, which enables a process for making wood composites without the use of formaldehyde.

The occurrence of water-soluble linear and branched HMF oligomers in solutions of HMF is, for example, from the DE 10 2014 112 240 A1 known. The formation of the HMF oligomers can be followed, for example, by means of HPLC analyzes.

In contrast to HMF monomers, HMF oligomers in the sense of the present invention are compounds of at least two linked HMF units / monomers. HMF oligomers are usually understood to mean compounds with a molecular weight of up to 3000 g / mol. Particularly suitable for the process are HMF oligomers with a low molecular weight which are soluble or at least dispersed in the chosen solvent under the chosen reaction conditions. The transition between dissolved and dispersed form can be fluid here, so that no distinction should be made in this regard in the present invention.

The polycondensation for providing the thermally curable resin is carried out in a manner known per se. Solvents suitable for the reaction and suitable reaction conditions such as, for example, reaction temperature and pH are known in principle to the person skilled in the art. The reaction is preferably carried out in an aqueous solvent.

It is self-evident for the person skilled in the art that the at least one HMF oligomer can be present in a mixture of HMF oligomers of different lengths and / or different degrees of crosslinking. It is also possible, by selecting an HMF oligomer or by selecting a combination of different HMF oligomers, to tailor the properties of the resin resulting from the preparation step to the technical intended use.

According to an advantageous embodiment of the process, the reaction for providing the resins is carried out at temperatures in the range from 40 ° C. to 140 ° C., preferably in the range from 50 to 140 ° C., more preferably in the range from 60 ° C. to 100 ° C. carried out particularly preferably in the range from 80 ° C. to 100 ° C. In principle, the temperature for carrying out the polycondensation can be varied within a wide range. However, it has been observed that more reactive resins can be obtained by the reaction at higher temperatures. Particularly highly reactive resins, which require short pressing times for curing during the subsequent formation of the wood-based materials, can be obtained at temperatures in the range from 80 ° C to 100 ° C. This was unexpected, since it was previously assumed that HMF decomposed at temperatures above 50 ° C.

According to a further advantageous embodiment of the method, the molar ratio of the amount of HMF used to the total amount of phenolic compound and / or aminoplast former is 0.20: 1 to 3: 1, preferably the molar ratio is 0.3: 1 to 1: 1 , the molar ratio is particularly preferably from 0.45: 1 to 0.70: 1. In principle, the molar ratio of the amount of HMF used to the total amount of phenolic compound and / or aminoplast former can be varied over a wide range. A molar excess of HMF can also be advantageous. A molar ratio suitable for the particular phenolic compound, the particular aminoplast former or for a mixture of phenolic compound and aminoplast former can be easily determined by the person skilled in the art.

According to a further advantageous embodiment of the method, the proportion of HMF oligomer is 0.05% by weight to 10% by weight, based on the total amount of HMF used, the proportion of HMF oligomer is preferably 0.1% by weight to 8 % By weight, based on the total amount of HMF used, particularly preferably the amount of HMF oligomer is 2% by weight to 4% by weight, based on the total amount of HMF used. Due to the high reactivity, small amounts of HMF oligomer are sufficient to provide reactive resins. It is obvious to the person skilled in the art that higher proportions of HMF oligomer can also be used. Also included in the invention is that the HMF oligomer makes up to or up to almost 100% by weight, based on the total amount of HMF used.

According to a further advantageous embodiment of the method, the HMF oligomer has 2 to 20 units, preferably 2 to 10 units, particularly preferably 2 to 4 units. HMF oligomers with 2 to 10 units are readily water-soluble under moderate conditions, i.e. at room temperature and under normal pressure, so that the HMF oligomers can be used for polycondensation in an aqueous medium without any problems. HMF oligomers with 2 to 4 units have improved water solubility. HMF oligomers with 2 units are particularly water-soluble and are therefore particularly suitable for the reaction.

According to a further preferred embodiment of the method, the HMF oligomer used for the reaction is a carbon-linked HMF oligomer. For the purposes of the present invention, HMF oligomers are referred to as carbon-linked HMF oligomers if at least two HMF units are linked via a carbon-carbon bond, including an aromatically bound carbon atom at position 3 or 4 of the furan ring, of one of the two HMF units . In particular, the carbon-linked HMF oligomer contains at least one first unit, the aldehyde group carbon atom of which is linked to an aromatically bound carbon atom of the furan ring of a second unit.

The inventors have found that in addition to HMF oligomers which result from the linkage of aldehyde and / or hydroxyl groups of the HMF units and which have the corresponding ether, hemiacetal and / or acetal bonds, both under acidic and form HMF oligomers under basic conditions, in which units are linked via a carbon-carbon bond. These bonds can arise, for example, when an aldehyde group of a first HMF monomer or an HMF unit of an HMF oligomer is electrophilically attacked on the carbon atom in position 3 or 4 of a furan ring of a second HMF monomer or an HMF unit of an HMF oligomer.

The mechanisms proposed for the formation of HMF oligomers in acid and in alkaline can Figures 1 and 2nd be removed. From these it can be seen, inter alia, that HMF oligomers which are linked by a carbon-carbon bond also have more free functional aldehyde and / or hydroxyl groups than HMF oligomers in which the compound is only present comes about via aldehyde and / hydroxyl groups of the HMF. This results in very reactive HMF oligomers that have additional crosslinking options.

The carbon-linked HMF oligomer may contain, in addition to the bond formed using an aromatically bound carbon, other bonds such as ether, hemiacetal and / or acetal bonds.

To increase the reactivity of the resulting resin, it is sufficient if two of the HMF units are already linked, including an aromatically bound carbon atom. In particular, carbon-linked HMF oligomers with 2 units contain a comparatively high proportion of free functional, reactive groups per HMF oligomer. The carbon-linked HMF oligomer can also have several such carbon-carbon linkages.

In addition to the carbon-linked HMF oligomers, further HMF oligomers with ether, hemiacetal and / or acetal bonds can also be present. Due to the high proportion of free functional groups, even small amounts of carbon-linked HMF oligomer are sufficient to provide very reactive oligomers. Also included in the invention is that the carbon-linked HMF oligomer makes up to or up to almost 100% by weight, based on the total amount of HMF oligomer.

The polycondensation-capable phenolic compound and / or the aminoplast former can be those which are usually used for the production of thermally curable resins.

Suitable polycondensation phenolic compounds are in principle all aromatic compounds bearing hydroxyl groups which have at least one carbon atom in the aromatic which is suitable for a nucleophilic addition reaction between the phenolic compound and the HMF.

The polycondensation-capable phenolic compound is advantageously phenol, lignin, a phenolic compound derived from lignin, resorcinol, hydroquinone, hydroxyhydroquinone, pyrocatechol, phloroglucin or a mixture of at least two of these compounds.

The aminoplast former is advantageously urea, melamine, substituted melamine, substituted urea, acetylene diurea, guanidine, thiourea, thiourea derivative, diaminoalkane, diamidoalkane or a mixture of at least two of these aminoplast formers.

In addition to the components mentioned, other phenolic compounds and / or aminoplast formers may also be present.

Depending on the phenolic compound and / or the aminoplast former, the pH in the preparation step can vary over a wide range. The pH can be, for example, in the range from 6 to 10, preferably in the range from 7 to 8.5.

According to a further advantageous embodiment of the method, the preparation step is carried out in a solution until the solution has reached a desired viscosity or the reaction is complete. The preparation step is preferably carried out until the solution has reached a viscosity of over 200 mPa.s, particularly preferably until the solution has reached a viscosity of over 450 mPa.s.

Advantageously, very reactive, thermally curable resins are provided which, by curing in contact with a lignocellulose-containing material, provide wood composite materials with very good mechanical properties.

The thermally curable resin preferably comprises at least one polymer obtained by polycondensation of phenolic compounds and / or aminoplast formers with 5-hydroxymethylfurfural (HMF), the polymer being a polycondensation product of a phenolic compound and / or an aminoplast formant with an HMF oligomer.

For the purposes of the present invention, the term polymer is understood to mean products of polycondensation. The polymers are usually water-insoluble.

The polymer is particularly preferably a polycondensation product of a phenolic compound and / or an aminoplast former with a carbon-linked HMF oligomer which contains at least one first HMF unit which is linked to an aromatically bound carbon of a second HMF unit.

The solids content of the resin obtained in the preparation step can be varied over a wide range. The solids content is at least 40% by weight. The solids content of the resin is preferably in the range from 45 to 80% by weight, particularly preferably between 50 and 70% by weight.

According to a further advantageous embodiment of the method, the method contains at least one further step which provides 5-hydroxymethylfurfural, which comprises at least one HMF oligomer, for the step of providing the thermally curable resin.

The provision step preferably includes exposing a more or less pure solution of HMF monomers and / or HMF oligomers to conditions which lead to the formation of HMF oligomers. The inventors have found that aqueous HMF solutions, which have been prepared, for example, from crystalline HMF with water, age to form the HMF oligomers. The amount and the molecular weight of the HMF oligomers can be determined here using analysis means familiar to the person skilled in the art, such as HPLC and NMR spectroscopy.

The formation of HMF oligomers under moderate conditions, that is, under normal pressure and room temperature, can be in the range of hours, days or weeks.

The conditions to which the HMF solution is exposed particularly preferably comprise alkalization or acidification of the solution. The conditions also particularly preferably comprise heating the solution, optionally in combination with acidification or alkalization. The aging process can be accelerated by acidification, alkalization and heating.

A particularly preferred variant of the step of making available involves 5-hydroxymethylfurfural, which comprises at least one HMF oligomer, by treating an aqueous suspension of cellulose-containing biomass and / or an aqueous carbohydrate solution of at least one hexose and / or an aqueous 5-hydroxymethylfurfural solution under hydrothermal conditions.

The treatment of biomass such as vegetable raw materials, of carbohydrates or of compounds derived from carbohydrates under hydrothermal conditions to obtain 5-HMF is known and provides for the starting material to be exposed to pressure and elevated temperature in an aqueous medium. When treating an aqueous suspension of cellulose-containing biomass and / or an aqueous carbohydrate solution of at least one hexose and / or an aqueous 5-hydroxymethylfurfural solution under hydrothermal conditions, HMF oligomers are formed.

Cellulose-containing biomass, which is often a waste product from agricultural producers, is particularly preferred due to its low cost factor. Preferred hexoses are fructose or glucose, in particular fructose or mixtures of fructose and glucose.

Preferred hydrothermal conditions are saturated steam pressure and temperatures of 150 to 250 ° C. This has the advantage that the formation of HMF oligomers is completed within minutes to a few hours, depending on the starting material.

The providing step is preferably carried out until the desired amount of HMF oligomer is reached or the reaction is complete.

The HMF, which comprises at least one HMF oligomer, is preferably present in aqueous solution at the end of the step of making available. It is further preferred to influence the content, the size and / or the concentration of the oligomer or oligomers. The content of the oligomer or oligomers is particularly preferably influenced by subjecting the solution obtained in the step of making available to a filtration of at least one filter medium. The treatment of an aqueous HMF solution after hydrothermal carbonization is, for example, in the DE 10 2014 112 240 A1 described.

According to a further advantageous embodiment of the method, the lignocellulose-containing material which is brought into contact with the resin comprises wood chips, wood fibers, wood flakes, wood chips, wood particles, wood strips, wood platelets and plates and mixtures thereof. The lignocellulose-containing material can vary in a wide range with regard to the large number of different wood composite materials.

The resin can be brought into contact with material containing lignocellulose by methods known to the person skilled in the art. Depending on the nature of the resin and the configuration of the lignocellulose-containing material, the contacting is usually carried out, for example by spraying on, brushing on, mixing with mechanical stirring or roller application.

According to a further advantageous embodiment of the process, the lignocellulose-containing material is resin in an amount of 2% by weight to 20% by weight, preferably in an amount of 5% by weight to 15% by weight, based on the weight of the dry lignocellulose-containing material , brought into contact. The amount of resin can vary over a wide range depending on the configuration of the lignocellulose-containing material and the requirements for the wood composite material. It may also be advantageous to bring mixtures of two or more resins into contact with the lignocellulose-containing material.

According to a further advantageous embodiment of the method, the curing of the resin comprises pressing the lignocellulose-containing material with the resin. Pressures of 1 to 30 mPa are usually used.

The pressing is preferably carried out at a temperature in the range from 120 ° C. to 250 ° C., particularly preferably in the range from 210 ° C. to 230 ° C. Due to the reactivity of the resins, just a few minutes are enough to obtain wood-based materials with good mechanical properties. The pressing time is preferably in the range from 3 to 10 minutes, particularly preferably the pressing time is in the range from 5 to 8 minutes. A short pressing time is advantageous from both a technical and economical point of view.

If desired, the crosslinking capacity of the resins can be increased by adding a hardener to the resins. The amount of hardener is preferably in the range from 2% by weight to 7% by weight, based on the amount of resin, particularly preferably in the range from 2% by weight to 5.5% by weight, based on the amount of resin, very particularly preferably in Range from 2 wt% to 3 wt%, based on the amount of resin. Hardeners can in particular be hexamethylenetetramine or ammonium salts such as ammonium sulfate. However, the reactivity of the HMF oligomers is so high that only very small amounts of hardener have to be used in order to obtain resins with a high crosslinking capacity. There is also no need for a hardener.

The wood composite materials obtained can finally be post-treated in a drying cabinet or wood dryer at temperatures in the range from 10 ° C. to 100 ° C. in a controlled atmosphere. Such can include, for example, a relative humidity in the range of 40% to 70%.

One advantage of producing a wood composite material using the method according to the invention is that the wood composite materials can be produced free of formaldehyde and on the basis of natural, renewable raw materials and have very good resistance to moisture, in particular water vapor. Another advantage of the process is that, due to the reactivity of the HMF oligomers, short pressing times in the minute range are sufficient to obtain a wood composite with very good mechanical properties. This is highly desirable from an economic point of view and with regard to the industrial manufacture of wood composite materials.

The following examples serve only to illustrate the invention and are not intended to limit it in any way.

Example 1: Production of chipboard a) Provision of an HMF solution with HMF oligomers:

A 16% aqueous solution of crystalline HMF was simultaneously concentrated and aged by concentrating it in a rotary evaporator at 45 ° C. and 30 mbar until the concentration of HMF was 50% by weight, based on the solution.

b) Preparation and comparison of the properties of urea HMF resins:

Two resins were made which differed in their molar ratio of urea to HMF. A first resin was produced with a ratio of 1: 0.5 urea to HMF, hereinafter referred to as UH (1: 0.5). A second Resin was produced in a ratio of 1: 0.25 urea to HMF, hereinafter referred to as UH (1: 0.25). The solids content of the resins was about 58%. 400 ml of the 50% HMF solution from a) were used for both resins. For both resins, the urea was reacted with HMF at a pH of 2 first for 2.5 hours and a temperature of 90 ° C. and then for several hours at a temperature of 20 ° C. The change in the viscosity of the resins was observed. Table 1: Viscosity increase as a function of time Time [hours] Viscosity [mPa.s] UH (1: 0.5) UH (1: 0.25) 4th 470 - 24th 1275 58 48 - 60 120 - 65 144 - 65 168 - 65

c) Pressing wood chips into chipboard:

Resin UH (1: 0.5) with a viscosity of 1275 mPa.s and resin UH (1: 0.25) with a viscosity of 65 mPa.s were used for the subsequent pressing of wood chips. The resins were mixed with the wood chips and with hexamethylenetetramine, respectively, and then pressed at 220 ° C. to produce 250 mm × 250 mm × 16 mm plates. The loading of the dry wood was 10% by weight resin solids, based on the amount of wood. In order to test the influence of different pressing times and different amounts of hardener, several plates were produced by varying the times and the amounts of hexamethylenetetramine. The values obtained with the two resins UH (1: 0.5) and UH (1: 0.25) for the chipboard are given in Table 2.

For comparison, a third resin, UH45 (1: 0.5), was made by reacting the components of the resin UH (1: 0.5) at a lower temperature of 45 ° C were. The resin UH45 (1: 0.5) was also used for pressing wood chips to 250 mm x 250 mm x 16 mm chipboard. The values obtained for these particle boards are also given in Table 2.

The comparison of the boards made with the resins showed that, in principle, better values for the internal strength are obtained with a longer pressing time.

With a molar ratio of urea to HMF of 1: 0.5, plates 3 and 4 achieve the high values of 52 N / mm ² and 55 N / mm ² . These values are due to a pressing time of 7.5 minutes in connection with a high manufacturing temperature of the resins of 90 ° C.

The plates 1 and 2 and 5 and 6 illustrate the influence of the temperature in the production of the resins.

Even plates made with smaller amounts of HMF give a satisfactory result when the pressing time is increased, as plates 7-10 show.

With regard to the hardener, it has been shown that different amounts of hardener make themselves less noticeable or not noticeable if the plates were produced with a certain proportion of HMF, as plates 3 to 6 show. The plates 7 and 10 with lower proportions of HMF are significantly more influenced by the amount of hardener. The values make it clear that due to the positive properties of the HMF oligomers used, the amounts of hardener required can be drastically reduced, whereby products with identical or comparable internal bond strength can be obtained.

wobei Fmax die Bruchkraft, a die Breite und b die Länge der Platte ist.Internal bond strength (IB) according to NF EN 319 (AFNOR 1993):
The internal bond strength in [N / mm ² ] is expressed by the following formula: $$\mathit{IB}=\frac{\mathit{Fmax}}{\mathit{axb}},$$

where Fmax is the breaking strength , a is the width and b is the length of the plate.

NF EN 319 (AFNOR 1993) specifies an internal bond strength of ≤0.35 N / mm ² for chipboard and fiberboard with a thickness in the range from 13 mm to 20 mm.

The plates for examining the internal bond strength were obtained by cutting from the plates produced under c). Their size was 50 mm x 50 mm. Before cutting, the plates were stabilized in a dryer at 20 ° C and a relative humidity of 65%.

The plates were attached to a base using a hot melt adhesive. The determination of the internal bond strength was carried out according to NF EN 319 (AFNOR 1993) by machine perpendicular to the plane of the plates. Table 2: Parameters of chipboard production and properties of the chipboard plate resin Synthesis temperature [° C] Viscosity [mPa.s] Molar ratio urea: HMF Pressing temperature [° C] Pressing time [min] Harder [%] Density [kg / m ³ ] Inner bond strength (IB) [N / mm ² ] 1 UH45 (1: 0.5) 45 382 1: 0.5 220 5.5 5 733 0.27 2nd UH45 (1: 0.5) 45 382 1: 0.5 220 5.5 2.5 729 0.21 3rd UH (1: 0.5) 90 1275 1: 0.5 220 7.5 5 717 0.55 4th UH (1: 0.5) 90 1275 1: 0.5 220 7.5 2.5 718 0.52 5 UH (1: 0.5) 90 1275 1: 0.5 220 5.5 5 715 0.43 6 UH (1: 0.5) 90 1275 1: 0.5 220 5.5 2.5 718 0.43 7 UH (1: 0.25) 90 65 1: 0.25 220 7.5 5 714 0.44 8th UH (1: 0.25) 90 65 1: 0.25 220 6.5 5 715 0.39 9 UH (1: 0.25) 90 65 1: 0.25 220 5.5 5 712 0.31 10th UH (1: 0.25) 90 65 1: 0.25 220 7.5 2.5 713 0.36

Further advantages and advantageous configurations can be found in the claims and the drawing below.

Figur 1

einen vorgeschlagenen Mechanismus der Kohlenstoff-Kohlenstoff-Bindungsbildung unter sauren Bedingungen anhand der Dimerisierung zweier HMF-Moleküle, sowie

Figur 2

einen vorgeschlagenen Mechanismus der Kohlenstoff-Kohlenstoff-Bindungsbildung unter basischen Bedingungen anhand der Dimerisierung zweier HMF-Moleküle.

Show it

Figure 1

a proposed mechanism of carbon-carbon bond formation under acidic conditions based on the dimerization of two HMF molecules, and

Figure 2

proposed a mechanism of carbon-carbon bond formation under basic conditions based on the dimerization of two HMF molecules.

All features of the invention can be essential to the invention both individually and in any combination.

Claims (13)

1. A method for producing wood composite materials, including the steps:

   - preparing a thermosetting resin by reacting a polycondensation-capable phenolic compound and/or an aminoplast-forming agent with 5-hydroxymethylfurfural (HMF) to form polycondensation products under conditions leading to the formation of polycondensation products,

   - bringing the resin into contact with lignocellulose material, and

   - curing the resin to form the wood composite material,

   characterized in that the 5-hydroxymethylfurfural comprises at least one HMF oligomer.
2. The method according to claim 1, characterized in that the reaction for preparation of the resins is carried out at temperatures in the range of 40°C to 140°C.
3. The method according to claim 1, characterized in that the proportion of HMF oligomer is 0.05% by weight to 10% by weight, based on the total amount of HMF used.
4. The method according to any one of the preceding claims, characterized in that the HMF oligomer has 2 to 20 units.
5. The method according to any one of the preceding claims, characterized in that the HMF oligomer is a carbon-linked HMF oligomer.
6. The method according to any one of the preceding claims, characterized in that the polycondensation-capable phenolic compound is phenol, lignin, a phenolic compound derived from lignin, resorcinol, hydroquinone, hydroxyquinone, pyrocatechol, phloroglucinol or a mixture of at least two of these compounds.
7. The method according to any one of the preceding claims, characterized in that the aminoplast-forming agent is urea, melamine, substituted melamine, substituted urea, acetylenediurea, guanidine, thiourea, thiourea derivative, diaminoalkane, diamidoalkane or a mixture of at least two of these aminoplast-forming agents.
8. The method according to any one of the preceding claims, characterized in that the preparation step is carried out in a solution until the solution has attained a desired viscosity or the reaction has ended.
9. The method according to any one of the preceding claims, characterized in that the method includes at least one further step, which makes available 5-hydroxymethylfurfural, comprising at least one HMF oligomer, for the preparation step.
10. The method according to claim 9, characterized in that the 5-hydroxymethylfurfural is supplied by treatment of an aqueous suspension of cellulosic biomass and/or of an aqueous carbohydrate solution of at least one hexose and/or one aqueous 5-hydroxymethylfurfural solution under hydrothermal conditions.
11. The method according to any one of the preceding claims, characterized in that the lignocellulosic material, which is brought into contact with the resin, comprises wood shavings, wood fibers, wood flakes, wood chips, wood particles, wooden strips, wooden disks and wooden plates as well as combinations thereof.
12. The method according to any one of the preceding claims, characterized in that the lignocellulosic material is brought into contact with the resin in an amount of 2% by weight to 20% by weight, preferably an amount of 5% by weight to 15% by weight, based on the weight of the dry lignocellulosic material.
13. The method according to any one of the preceding claims, characterized in that the curing of the resin comprises pressing the lignocellulosic material with the resin.

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